The present invention relates to an outside filter, in particular for an aquarium.
In such outside filters, the motor operated pumps are not self-aspirating. The reason is that during certain conditions, for example when the pump is turned off, the water supply through the supply conduit to the pump chamber which accommodates the impeller of the pump is interrupted, and air is supplied in and then during subsequent turning on the pump can not transport water. Filter devices are known, which are provided with a device for producing a vacuum which operates when needed and therefore water can be aspirated in the air which is contained in the supply conduit with displacement. These devices are composed for example of a hand pump provided with a flexible bellows and various valves and conduits. The handling of such devices is partially very expensive and not practical.